SYDNEY—Coca-Cola Co. has placed a $500 million bet that it can re-energize sales of its soda brands in Southeast Asia, which have faced stronger competition from rivals based in countries including Japan and Peru.

The Atlanta-based beverages giant agreed to buy a 29.4% stake in the Indonesian business of Coca-Cola Amatil Ltd., which plans to use the funds on new factories, warehouses and fridges that house its products in gas stations and convenience stores. Coca-Cola Amatil—itself 29%-owned by Coke and operating as its Australian...